Arsenorgano-Verbindungen : XXII. Zur synthese der 1,3-benzazarsoline

o-Aminophenylarsine is prepared by reduction of o-nitrophenylarsonic acid. Metallation and subsequent treatment with alkyl halides give the secondary o-aminophenylarsines. o-Aminophenylarsines react with aldehydes, ketones and ketoesters forming derivates of the 1,3-benzazarsoline. Exceptions are redox reactions between o-aminophenylarsine and aldehydes. The properties of the compounds are described in more detail.     

Stereochemistry of the Reactions of Cyclic Ketones with Lithium Aluminum Hydride and Methyllithium. IV. The Stereochemistry of the Reactions in 2,2-Dimethyl-4-t-Butylcyclohexanone Systems

Previous publication showed that the stereochemistry of lithium aluminum hydride reduction of cyclic ketones can be evaluated by the use of an empirical equation, . This paper reports further test of this relationship in the new system of 2,2-dimethyl-4-t-butyl-cyclohexanone. Lithium aluminum hydride reduction of this ketone yields 95.6% trans-alcohol (lit., 95.9%) corresponding to D?(D?G*)_H of 1.67 Kcal/mol. With methyllithium, the ketone formed 77.5% of trans-alcohol (D?(D?G*)_D?fs = 0.67 Kcal/mol). These data give a calculated D?G* = 0.74 Kcal/mol which agrees well with the literature value of 0.87 or 0.28 Kcal/mol. Structural assignments of 2,2-dimethyl-4-t-butylyclohexanone, 1,2,2-trimethyl-cis- and trans-4-t-butylcyclohexanols by pmr spectroscopic method are also given.     

Synthesis and Stereochemistry of Substituted 1,3-Dioxa-2-silacyclohexanes: VII. Synthesis and Stereochemistry of Substituted 2-Vinyl-2-methyl-1,3-dioxa-2-silacyclohexanes

The stereochemistry of substituted 2-vinyl-2-methyl-1,3-dioxa-2-silacyclohexanes was studied by ^1Hand ^13C NMR spectroscopy. The configurational and conformational assignment of a mixture of 2-vinyl-2,4-dimethyl-1,3-dioxa-2-silacyclohexane diastereomers with various ratios of the cis and trans forms was made. The molecules of both conformers occur chiefly in the chair conformartion with equatorial location of the methyl group at the C⁴ atom. The experimental data were confirmed by AM1 and MM+ optimization of the molecular geometry.     

The Conversion of 1,3-Cyclooctadiene to 1-Vinylcyclohexene

Meroquinene (1), a key degradation product of quinine and an important intermediate in the preparation of the cinchona and other alkaloids,¹ has only recently been synthesized ² even though attempts were made at its preparation for over thirty years. These early attempts were frustrated primarily by the difficulty encountered in the introduction of a potential vinyl group onto a piperidine ring. Alkylation of 3-car-bethoxy-N-benzoyl-4-piperidone (2) with either phenoxyethyl chloride³ or dimethylaminoethyl chloride (3)⁴ resulted in exclusive formation of the O-alkylated product, even though alkylation of the presumably analogous 2-carbethoxycyclohexanone with 3 gave nearly equal amounts of C- and O- alkylated materials.⁴ The use of other piperidone derivatives in this reaction was precluded by the report that attempts to alkylate 3-car-bethoxy-N-alkyl-4-piperidones gave only the quaternary nitrogen product.⁵     

化学教学中的信息转换

教学的本质是信息的传输、加工和内化的过程。信息转换是知识再生产与生产新知识相融合的一个思维过程。分析了信息呈现的多种方式, 从“信息量多少、信息表征方式、信息的属性”等方面阐述了信息的转换方法策略。     

1,3-Diphenylpropane-1,3-diamines XI. Conversion of a 3-hydroxy-1,3-diphenylpropan-1-one to 1,3-diphenylpropane-1,3-diamines

Summary Highly diastereoselective BH₃/THF syn-reduction of the 3-hydroxy-1,3-diphenylpropan-1-one/BBr₃ complex3/BBr₃ (cf.Sarko) afforded themeso-diol4, whereas racemate5 was obtained by BH₃/THF reduction without complexation. Mesylation, exchange of mesylate by azide, and reduction with SnCl₂/thiophenol led to the diamines10 and11 which were also produced by reductive N-N cleavage of the 4,5-dihydropyrazole13.Dedicated to Prof. Dr.G. Wurm, Berlin, on the occasion of his 60^th birthday     

高中化学竞赛中的立体化学解读

对高中化学竞赛试题中有关立体化学试题进行归类解读, 帮助参加化学竞赛的指导教师和同学形成解答此类试题的一般方法, 并对今后的该类化学竞赛试题进行展望。     

Synthesis and Stereochemistry of Some New Spiro-1,3-perhydrooxazines

Summary.  The synthesis and the stereochemistry of new spiro-1,3-perhydrooxazines are reported. The stereoisomerism of these compounds is discussed considering the data of conformational analysis, the helical chirality of the spiro[5.5]undecane skeleton, and the triligand virtual chiral center belonging to the 1,3-perhydrooxazine ring. Received February 21, 2000. Accepted (revised) April 18, 2000     

Synthesis and Stereochemistry of Some New Spiro-1,3-perhydrooxazines

 The synthesis and the stereochemistry of new spiro-1,3-perhydrooxazines are reported. The stereoisomerism of these compounds is discussed considering the data of conformational analysis, the helical chirality of the spiro[5.5]undecane skeleton, and the triligand virtual chiral center belonging to the 1,3-perhydrooxazine ring.     

Chemistry of 1,3-diarylpropynones in superacids

In superacids with H0=-14 to -20, it has been found that 1,3-diarylpropynones ArC triple bond CCOAr' are either protonated on oxygen of carbonyl groups with the formation of stable ions ArC triple bond CC(O+H)Ar' or undergo further transformations when the highly conjugated system is electron-rich enough. In the latter case, 3-arylindenones are produced very rapidly and with high efficiency (up to 95% yield in less than 30 min). The influence of the substituents Ar, Ar' and of the reaction conditions on the behavior of 1,3-diarylpropynones and on the intramolecular cyclisation have been studied. From the collected data, a mechanism has been proposed involving vinyl cations ArC+=CHCOAr' and/or dications ArC+=CHC(O+H)Ar'.     

Synthesis and Stereochemistry of Some New 1,3-Oxathiane Derivatives

Summary. The synthesis and stereochemistry of some new 2,5-substituted 1,3-oxathiane derivatives are reported. The anancomeric or flexible structure of the derivatives and some peculiar cases of prochirality are revealed by NMR investigations.     

碱性体系氢化物发生-原子荧光光谱法测定矿物中的痕量硒

对碱性氢化物发生－原子荧光光谱法测定痕量硒的方法进行了探讨,研究了体系的最佳实验参数。与常规酸性 体系氢化物发生－原子荧光光谱法比较,本法能有效地消除大量铜、铁、钴、镍等过渡族元素的干扰,样品可不经分离直接进行测定。经过国家标样的分析验证,其测定值与推荐值吻合。方法的检出限为0.55ug/L,相对标准偏差为4.12％;原子加入回收率为99.8%.     

Synthesis of Monolithic Silica Gel in Alkaline Medium

The influence exerted by the basicity and nucleophilicity of a number of organic amines on the formation of a monolithic silica gel by the organic sol-gel method was studied.     

Synthesis of new 1,3-oxaphosphorinanium salts. Stereochemistry of hydroxide-induced displacement of methoxide ion

[reaction: see text] The synthesis of pure cis- and trans-3-methoxy-2,2,6-trimethyl-3-phenyl-1,3-oxaphosphorinanium tetrafluoroborate salts 3a and 3b, respectively, molecules designed to evaluate the effect of oxygen on the steric course of base-induced nucleophilic displacement of the methoxy group at phosphorus, was accomplished. It was found that these isomeric salts react with aqueous sodium hydroxide to produce the corresponding phosphine oxides 7a and 7b with complete retention of configuration at phosphorus.     

竹红菌甲素在碱性和中性溶液中的结构变化

竹红菌甲素(简称甲素,HA)是从我国云南省的一种真菌——竹红菌中提取出来的主要光敏色素。竹红菌乙素(简称乙素,HB)是竹红菌中另一个比甲素少得多的光敏色素。甲素在酸性条件下可以转化成乙素,但产率不高。下面讨论甲素在碱性和中性溶液中的结构变化,提供从甲素制备乙素和I的简便方法。